no longer records video

My CanonMV500 suddenly went black in the middle of a recording but cont. to record audio. After a couple of minutes it came back again.
Next time I used it, it was black right from the beginning, and after some time the video came back but now its definitely gone. Everyhting else works, it still continues to record the audio so the tape and everyhting are working.
Any suggestionson what I can try....before I have to go a very expensive repair job???